Method to control light relays



p 1931. F. SCHROETER 1,821,948

METHOD TO CONTROL LIGHT RELAYS Filed April l8, 1927 5 cm'sm 2 2 /0-RECEIVER 4 OJCILLATQR' A5; ii SCEEEN' AMPL/F E/e INVENTQ R FRITZSCHRUETER A ORNEY Patented Sept. 8, 1931 NETE STATES FRITZ SCHROETER, OFBERLIN, GERlvIANY, ASSIGNOR TO GESELLSG'HAFT FOR BRAKE.-

LOSE TELEGRAPHIE M. B. H., OF BERLIN, GERMANY, A CORPORATION OF GERMANYMETHOD TO CONTROL LIGHT RELAYS Application filed April 18 1927, SerialNo. 184,560, and in Germany May 20, 1926.

It is well known that by means of modulated high-frequency oscillationscontrol actions may be produced upon polarized light by the use of thevibrations of piezo-electric crystals, with the result that the color orthe intensi-- y or brightness of the light is varied at the rhythm ofthe modulations as has been set forth in patent application Serial No.171,583, filed February 28, 1927, by

Alexander Meissner. The action thus brought upon ihe polarized lighttakes place upon passage of light through the quartz by virtue of theresultant optical anisotropy, or else the oscillating quartz crystalserves 5 merely as ihe exciter of anisotropy in other media subject tothe penetration of light, for instance, glass, by the mechanicaltransmission oscillations. The invention refers to all of thesearrangements and schemes. The

2 basic idea of the invention is as follows:

In order to cause the quartz crystal to oscillate, it has heretoforebeen necessary to have at disposal a separate highly constant radiofrequency source, being mostly in the shape of a small tube generatorsupplying a wave equal to the natural period of 0scillation of thequartz crystal. In order to avoid this complication, the present invention which is particularly useful and adapted so for short-wave work intransmission operates in this manner that from the high-frequency, byvirtue of interference, heterodyne or beat action, the excitingfrequency of the quartz crystal is directly obtained and is furtheramplified as such, until the oscillation amplitude is raised to a pointfor adequate excitation of the quartz crystal. Since means adapted tofar-reaching amplification of radio frequency energy without incurringthe risk of self-oscillations are now known (for instance, neutrodynecircuits, compensation arrangements, etc.), the basic idea of theinvention is performable without any difiiculties. The frequencyobtained by heterodyne 415 action equals the natural period of thequartz crystal and contains directly the controlling modulations whichby the aid of the light relay are changed into corresponding lightvanations.

5 The invention has been illustrated conventionally by the accompanyingdrawings, wherein:

Fig. 1 illustrates a suitable form of receiving apparatus forinfluencing the crystal; and,

Fig. 2 illustrates conventionally a suitable form of optical system foruse with a crystal or the type shown in Fig. 1.

Now referring to the drawings, signals of any character desired forreception are received by the conventionally indicated receiving meansof Fig. 1, comprising an antenna 1 and a receiver 2, from which they aretransferred through a transformer 3, for example, to an amplifiercircuit l including a triode amplifier 5. Associated with the triodeamplifier circuit 4 is an oscillator 6 of any desired and suitablefrequency which when impressed upon the input circuit of the triodeamplifier through transformer 7, for example, together with the receivedsignals produces a heterodyne beat note of a frequency suitable forvibrating or oscillating the crystal 8 which is connected with theoutput circuit of the triode 5, as shown, or, if desired, of a differenttriode where a plurality of amplifiers are used. The triode 5 isarranged to amplify the exciting frequency for the crystal until theoscillation amplitude is raised to such a point that adequate excitationmay be obtained.

The accompanying drawings show the crystal 8 connected in the outputcircuit of the amplifier triode 5 across a resistance 9 and the excitingfrequency is applied to the crystal 8 by means of the electrodes 10 and10.

As the exciting frequencies are applied to the crystal, the polarizedlight passing therethrough is doubly refracted in well known manner asshown, for example, by British Patent No. 266,753. A suitable form ofoptical system for an arrangement of this type is illustrated by Fig. 2,wherein light from a source 11 is directed by means of a lens 12 througha diaphragm 13 to a polarizing nicol 1%. As the light polarized in oneplane leaves the nicol let it passes through the crystal 8, and thencethrough the analyzing nicol 15 which polarizes the light in a directionat right angles to the plane of polarization through the nicol 14, andthe light issuing beyond the analyzer 15 may then be directed to thescreen 16 in well known manner.

Having described my invention, I claim In combination with a radioreceiving system of the type including a receiving circuit and means forimpressing thereon received fluctuating signal energy together with alocal means for impressing thereon an electromotive force of a differentfrequency than the received fluctuating energy for producing a resultantbeat note from said received energy and an amplifying means for amplifying the resultantbeat note, a crystal light valve connected acrossthe'output of the amplifier for producing electric double refraction ofpolarized light beams passing therethrough in accordance withfluctuating potentials applied thereto from the amplifier, and aresistance coupling shunting said crystal for connecting a power supplywith the plate electrode of the said amplifier, the plate circuit ofsaid amplifier being free of extraneous inductance whereby thecharacteristics of said amplifier remain substantially uniform.

FRITZ scHRoTER.

